This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We have developed two new techniques for clinical imaging system based on light scattering spectroscopy (LSS). The size of the excitation beams is 2cm square and its wavelength is stepped from 450nm to 700nm with 5nm per step. The light backscattered from the top layer of the sample along with the diffusive reflectance from the underlying layer of the sample is detected by a CCD to provide images of the sample. The spectrum is taken on each pixel of the CCD for later analysis. The first technique is spatial gating. The excitation beam is embedded with dark areas which are not illuminated. The signal detected from dark areas contains the diffusive reflectance from the underlying layer of the sample. Therefore, the signal from the illuminated areas minus the one from the adjacent dark areas provides the light scattered from the top layer of the sample. The second technique is size discriminating polarization gating. To perform this method, two images are taken for each wavelength. The collection is with the polarization parallel to the excitation which is linearly polarization horizontally or vertically for corresponding images. The contributions to the difference between two measurements from scatterers will vary with their size. This technique can be used to enhance the signal from scatterers with certain range of sizes while suppress the signal from scatterers with different sizes. To demonstrate these techniques, we have measured the reflectance signal from a suspension with polystyrene beads on top of an intralipid gel providing diffusive background. There are two size groups of beads in suspension. One is with diameters around 10 um and another is with diameters around 1 ?m. We show that we can single out the single backscattering from 10 um beads from both the single backscattering from 1 um beads and the diffusive background from intralipid. The goal of this project is to develop new and complimentary techniques along with algorithm for the clinical LSS imaging system suitable for clinical setting to do clinical study. Current effort is underway to develop theoretical model by using polarized Monte Carlo simulation. By comparing the prediction from the theoretical model and experimental results, we can then develop the algorithm for tissue parameter extraction to provide cell morphological information that allows for accurate early diagnosis of dysplastic regions.
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